our pentagon correspondent barbara starr's been watching what's going on. barbara, what is the u.s. military most concerned about right now? >> wolf, as they watch that call-up of 75,000 israeli reservists, that is the concern. is this leading to a ground war? we've talked to officials here who say the major concern israel will move in on the ground. and that will be a significant escalation that will reverberate throughout the region. so here's the calculation. how far will hamas go in continuing its rocketed mortar attacks into israel? they know that if they pull back, the israelis presumably will pullback and this dangerous escalation can be avoided. if there is a ground war, if israeli troops cross that border, the tanks and troops, and go into gaza, the next concern is what egypt will do. egypt's new government very fragile. will it feel the pressure to move? will it come into sanai, all of this now at the end of a long week in washington. >> diplomats in the region and around the world are working hard behind the scenes to stop this from becoming an all-out war. what are you h